The crystal distortion resulting from long-range order in vanadium carbide

Abstract

A Guinier X-ray camera has been used to determine the cubic sublattice distortion which accompanies carbon atom/vacancy ordering in vanadium carbide crystals of composition between VC₀.₇₈ and VC₀.₈₄. The metal atom sublattice is reduced to rhombohedral symmetry with unit-cell angle 90·12 ± 0·03°. The internally twinned, lenticular plate-like morphology and specific habit plane observed in partially transformed crystals may be explained by the reduction in strain energy associated with interfaces between the long-range ordered phase and the cubic matrix.